The quality of the picture taken with the camera is influenced by the properties of the camera and the optical system. The sensor of a digital camera has a certain resolution and certain characteristics, which define the quality of the image photographed. Among the optical features, the image angle, zoom and focal length influence the image quality particularly in small cameras, whose features cannot be infinitely improved due to the small device size. In addition, the optical system always introduces distortions. Some of the distortions are compensated by optical means, such as by installing an optical element of the opposite sign for correcting the distortion caused by the optical element. Optical distortions can also be compensated by taking into account characteristics of the objective, such as light distribution, in the image processing. Typically optical distortions are programmably corrected in digital cameras. The image quality is also essentially affected by the user's skills, as the user often selects certain parameters having a direct or an indirect effect on the image quality. In addition, for example waggling of the camera at the moment of taking the picture causes blurring in the final picture.
Optical systems can never be made completely distortionless. Therefore, achieving an acceptable level of image quality is generally aimed at. Correction of some of the distortions leads to an excessive increase in the total weight or costs of the device, for example, and is therefore not sensible. An acceptable image quality depends on the application, targets and purpose of use. For example, a different level of image quality is required from a professionally used camera compared to a small camera for general purpose, such as a camera installed in a mobile phone. Correction of the image quality is typically a compromise between the desired result, on one hand, and the costs and size of the device, on the other. Then again, the final image can today be further processed programmably for achieving the desired result.